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Create attachment_pdf_invoice_generator.yml #3716

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Create attachment_pdf_invoice_generator.yml
JFarina5 Dec 29, 2025
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Dec 29, 2025
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54 changes: 54 additions & 0 deletions detection-rules/attachment_pdf_invoice_generator.yml
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name: "Attachment: PDF with invoice generator default metadata"
description: "Detects single-page PDF attachments with suspicious metadata characteristics common in invoice scam campaigns, including ReportLab with default titles, OpenPDF with missing creators, or specific LibreOffice Draw versions, sent from free email providers or with missing recipients."
type: "rule"
severity: "medium"
source: |
type.inbound
and any(filter(attachments, .file_extension == "pdf"),
// single page, nonlinearized PDFs
beta.parse_exif(.).page_count == 1
and coalesce(beta.parse_exif(.).linearized, "No") == "No"
// exclude legit invoice platforms
and not strings.icontains(beta.parse_exif(.).producer,
"OpenPDF 1.0.0-SNAPSHOT"
)
and (
// ReportLab with default "untitled" title
(
strings.icontains(beta.parse_exif(.).producer, "ReportLab")
and beta.parse_exif(.).title == "untitled"
)
// OpenPDF with empty creator
or (
strings.icontains(beta.parse_exif(.).producer, "OpenPDF")
and coalesce(beta.parse_exif(.).creator, "") == ""
)
// LibreOffice Draw, specific version seen in invoice scams
or (
strings.istarts_with(beta.parse_exif(.).producer,
"LibreOffice 25.8"
)
and beta.parse_exif(.).creator == "Draw"
)
)
)
and (
headers.return_path.domain.root_domain in $free_email_providers
or any(headers.reply_to, .email.domain.root_domain in $free_email_providers)
or length(recipients.to) == 0
)

attack_types:
- "BEC/Fraud"
- "Callback Phishing"
- "Credential Phishing"
- "Malware/Ransomware"
tactics_and_techniques:
- "Evasion"
- "PDF"
- "Free email provider"
detection_methods:
- "File analysis"
- "Header analysis"
- "Sender analysis"
id: "16dc706e-cc48-57cb-8098-953364c1134e"